1. Field of the Invention
The present invention relates to an ophthalmic treatment apparatus, and more particularly to an ophthalmic treatment apparatus that uses laser light.
2. Description of the Prior Art
The manifestation of neovascular tissues in retinal lesions or degeneration in the eye fundus can indicate the progress of a disease. Various treatment methods have been tried for removing neovascular tissues. These include surgery to remove the neovascular tissues, the use of laser coagulators, and, more recently, treatment using the drug Interferon, and radiation treatment. The problem with surgery is that it is an invasive method that also damages normal tissue, leaving after-effects such as a deterioration in visual acuity. The success rate with treatments using drugs or radiation cannot be described as very high, either, and there are concerns about after-effects and side effects.
At present the laser coagulator method is considered the surest, but the heat of the laser beam scorching the retina can result in a loss of function by cells in the coagulated portion, thereby degrading vision. That is, the problem with the laser coagulation method is that technically it is virtually impossible to coagulate just the neovascular tissues without at the same time destroying normal cells in the vicinity of the vascularized region.
To address this problem, the present applicants filed a joint application for a new ophthalmic treatment apparatus that utilizes a photochemical reaction between radiated light and a photosensitive substance (JP-A 9-173376). That apparatus employs a laser projector that utilizes a fundus camera optical system. The patient is administered a photosensitive substance or photosensitizer that accumulates specifically in the neovascular tissues. Then, when the neovascular portion fluoresces, the laser beam is focused on the fluorescing portion to thereby selectively destroy or seal the neovascular tissues.
However, although the above ophthalmic treatment apparatus is based on the photochemical reaction principle, the laser beam projected via the fundus camera optical system irradiates the eye fundus with a certain degree of divergence. As a result, it was found that because the tissues around the neovascular tissues in the fundus were also irradiated by the laser, there was also a possibility of impairment of the surrounding normal tissue. While fluorography using contrast medium is an effective way of determining the position of neovascular tissues in an affected region, some such fundus-camera based systems do not have the sufficient fluorographic resolving power or contrast required for diagnostic purposes, and real-time close-up observation of the affected area using a safe light-intensity level is also difficult.
An object of the present invention is to provide an ophthalmic treatment apparatus that enables real-time close-up observation of the eye fundus and simultaneously enables irradiation with the therapy laser beam, thereby making it possible to treat neovascular tissue lesions without affecting normal cells and go minimizing any reoccurrence of the condition.
In accordance with the present invention, the above object is attained by an ophthalmic treatment apparatus in which a laser beam from a laser light source is projected via an optical system onto an eye fundus of a patient""s eye for treatment thereof, comprising a laser light source that generates a laser beam having a predetermined wavelength, optical scanning means for deflecting the laser beam from the laser light source at a predetermined frequency to scan the eye fundus therewith, and output means for detecting an intensity of reflected light and fluorescent light from the eye fundus to output an image of the eye fundus based on the scanning by the optical scanning means, wherein a photosensitive substance that accumulates specifically in neovascular tissues is administered to the patient to define a region of the eye fundus including the neovascular tissue portion based on the eye fundus image, and the region thus defined is irradiated by the laser beam from the laser light source to cause a photochemical reaction between the photosensitive substance and the laser beam, thereby destroying or sealing off the neovascular tissues concerned.
The above object is also attained by an ophthalmic treatment apparatus in which a laser beam from a laser light source is projected via an optical system onto an eye fundus of a patient""s eye for treatment thereof, comprising a laser light source that generates a laser beam having a predetermined wavelength, optical scanning means for deflecting the laser beam from the laser light source at a predetermined frequency to scan the eye fundus therewith, output means for detecting an intensity of reflected light and fluorescent light from the eye fundus to output an image of the eye fundus based on the scanning by the optical scanning means, means for defining a region of the eye fundus including a neovascular tissue portion based on the eye fundus image obtained after a photosensitive substance that accumulates specifically in neovascular tissues has been administered to the patient, and means for amplifying a laser beam intensity during scanning of the defined region by the laser beam.
The basis of the invention is that after a photosensitive substance that accumulates specifically in the neovascular tissues has been administered to the patient and the photosensitive substance has accumulated in the neovascular tissues, a scanning laser ophthalmoscope is used to project a therapy laser beam at the region concerned. In accordance with this invention a scanning laser ophthalmoscope is combined with a laser system that outputs a high-power laser treatment beam. This makes it possible to accurately focus the therapy laser beam on the neovascular tissues while at the same time observing a close-up image of the eye fundus on a TV monitor. Thus, compared to a conventional eye fundus camera system, the system of this invention makes it possible to reduce the influence of the laser beam on the surrounding tissues, and thereby enables the neovascular lesion to be treated easily and reliably.
Further features of the invention, its nature and various advantages will become more apparent from the accompanying drawings and following detailed description of the invention.